Host plant resistance in Brachiaria grasses to the spittlebug Zulia colombiana

Twelve forage grass accessions including 11 accessions of Brachiaria Griseb, were evaluated in a glasshouse for host plant resistance to nymphs and tolerance to feeding damage caused by adults of Zulia colombiana (Lallemand) (Homoptera: Cercopidae). Resistance to nymphs was evaluated with a technique that provided uniform environmental conditions and abundant feeding sites. B. brizantha Stapf (cv. Marandú) was the most resistant of the accessions tested based on nymphal mortality, duration of nymphal stadia, and weight of adult females. Andropogon gayanus Kunth, resistant to spittlebug attack in the field, was susceptible under the conditions of this study. While growth habit and rooting characteristics may contribute to field resistance, other resistance factors are present within the genus Brachiaria, particularly in the case of B. brizantha cv. Marandú. The number of insect-days causing severe damage in the most tolerant species (B. dictyoneura Stapf and B. humidicola Schweick) was approximately six times greater than that necessary to cause the same level of damage to the most susceptible species (B. ruziziensis Germain & Evrard and B. decumbens Stapf). No difference was found in regrowth capacity between infested and noninfested plants within accessions. There was a significant positive correlation between number of insect-days causing severe damage (tolerance) and regrowth of infested plants.

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Résumé Brachiaria est une graminée fourragère prometteuse pour les sols tropicaux acides, saturés d'aluminium. Z. colombiana est un Cercopidae très répandu, limitant l'utilisation de Brachiaria en Amérique Latine. La résistance (antibiose et tolérance) à Z. colombiana, de Brachiaria d'origines diverses a été examinée. B. brizantha cv. Marandù s'est révélé le plus résistant d'après la forte mortalité larvaire, la prolongation du développement larvaire, et le poids réduit des femelles adultes de Z. colombiana. Andropogon gayanus, résistant dans la nature, s'est révélé sensible. Ces résultats suggèrent que cette résistance de A. gayanus dans la nature pourrait être due à la structure du végétal et à son mode de croissance. Dans le cas de B. brizantha cv. Marandù, des facteurs supplémentaires de résistance, mis en évidence à partir de différents modes de croissance, ont été éliminés, de façon à identifier les mécanismes de l'antibiose présents chez Brachiaria. Une grande gamme de résistance aux attaques alimentaires a été observée chez Brachiaria. Les plus résistants ont besoin de 6 fois plus de jours d'attaque par Z. colombiana pour provoquer les dégâts observés sur individus sensibles.

     

High-dose mode of death in Tribolium

This study reports the first demonstration within a single insect genus (Tribolium) of both the acute, or lethal-midlethal, dose-independent pattern of mortality, and the hyperacute, dose-dependent pattern, after appropriate doses of ionizing radiation. This demonstration provides resolution of apparently contradictory reports of insect responses in terms of doses required to cause lethality and those based on survival time as a function of dose. A dose-dependent mortality pattern was elicited in adult Tribolium receiving high doses, viz., 300 Gy or greater; its time-course was complete in 10 days, before the dose-independent mortality began. Visual observations of heavily-irradiated Tribolium suggested neural and/or neuromuscular damage, as had been previously proposed by others for lethally-irradiated wasps, flies, and mosquitoes. Results of experiments using fractionated high doses supported the suggestion that the hyperacute or high-dose mode of death is the result of damage to nonproliferative tissues. Relative resistance of a strain to the hyperacute or high-dose mode of death is not necessarily correlated with resistance to the midlethal mode, which is believed to be the result of damage to the proliferative cells of the midgut.

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Résumé Les résultats de nombreuses études des réactions des insectes adultes de différents groupes à l'irradiation s'opposent quant à l'importance de la dose provoquant la létalité et quant aux modalités de la mort. Les diptères et les guèpes impliquent des doses très élevées,-des centaines de Gy-, ne présentent aucune période caractérisant la mort par irradiation, et décèdent de plus en plus tôt avec l'augmentation des doses. Beaucoup d'autres insectes succombent à des doses (milétalelétale) beaucoup plus faibles,-de quelques Gy à des dizaines-, et quelle que soit la dose meurent au bout d'un temps voisin.Au cours de cette étude, nous avons pu observer que ces deux types de mortalité peuvent être provoqués chez le même genre d'insecte (Tribolium), avec des doses convenables d'irradiation . Un syndrôme caractéristique a été provoqué avec des doses très élevées, de 300 Gy ou plus,-à ces doses la mort est obtenue en 10 jours après l'irradiation. L'absence de syndrôme caractéristique se produit avec des doses inférieures ou égales à 80 Gy; la mort a lieu alors entre 10 et 16 jours en fonction de la dose.Les différences entre les deux types de décès indiquent deux processus de mort par irradiation. La manifestation d'une désorientation et d'une perte de coordination motrice chez les Tribolium fortement irradiés suggère des altérations neurales et/ou neuromusculaires comme cause/s de ce type de mort provoquée par des doses élevées. L'implication de tissus sans prolifération a été confortée par les résultats d'expériences utilisant de hautes doses fractionnées. Le type de mort milétal est considéré après de nombreuses observations indépendantes, comme le résultat d'atteintes à la prolifération des cellules de l'intestin moyen.Les données contradictoires sur les réactions des insectes aux irradiations proviennent d'abord de l'absence de connaissances sur le lieu des dégâts. Les diptères sont connus maintenant, après différentes études, comme perdant complètement l'aptitude au renouvellement cellulaire, et présentent ainsi un type de mort avec dose élevée. Beaucoup d'autres insectes adultes ont un renouvellement cellulaire de l'intestin moyen limité, et ainsi présentent le type de mort milétal. Le type de mort, dit haute dose, peut être induit dans cette dernière catégorie d'insectes par une irradiation suffisamment forte, et, dans le cas du Tribolium le déroulement de la mort se produit alors de deux façons bien distinctes.

     

Upstream-downstream movements of aquatic invertebrates in a Rocky Mountain stream

Simultaneous collections of drift and organisms moving either upstream or downstream in association with the substrate were made using a specially designed sampler. Samples were taken in a diel series along a transect across the study riffle of a Colorado foothills stream on six dates over an annual cycle. In addition to longitudinal movements, taxonomic composition and diel periodicity were evaluated. The insect-dominated fauna showed a net downstream displacement. Only the caddisflies Helicopsyche borealis and Hesperophylax occidentalis exhibited net upstream movement, primarily a result of low drift frequencies. The taxonomic composition of moving invertebrates differed from that of the benthos. Drift resembled downstream moving substrate-associated invertebrates in composition, but differed from that of the upstream directed fauna. Taxa collectively exhibited four types of diel patterns: 1) similar downstream (drift and substrate-associated movements) patterns, which generally differed from the upstream pattern; 2) similar benthic (upstream and downstream) patterns, which differed from that of drift; 3) aperiodic patterns; and 4) independent patterns for each type of directional movement. Analysis of size classes based on head capsule width for the mayfly Baetis tricaudatus showed significantly smaller size in stationary individuals compared with moving individuals in the population and revealed that nymphs moving during the day were smaller than those moving at night.     

Effect of Moniliformis moniliformis density on distribution within the definitive host population (Rattus norvegicus)

The population dynamics of Moniliformis moniliformis was studied in ‘free-ranging’ laboratory rats, Rattus norvegicus, presented with different relative density levels of M. moniliformis in cockroaches, Periplaneta americana. Changes in selected population parameters of the negative binomial distribution were evaluated as indicators of changes in aggregation. A significant increase in the degree of aggregation of parasites occurred as a result of the increase in relative density of infective stages available to the rats. This increase in aggregation was due to the increase in over-dispersion that occurred in female rats only. The degree of aggregation in females was found to be significantly higher than that in males at both treatment levels. The best indicators of the degree of aggregation were found to be the ratio of the variance to the relative density and the ratio of the log-variance to log-relative density. Changes in k were not correlated with changes in over-dispersion or the relative density.     

Scale insect allozyme differentiation within and between host trees

Summary Allelic frequencies and genotypic distributions in three polymorphic enzyme systems demonstrated genetic differentiation over extraordinarily short distances in a population of black pineleaf scale insects infesting ponderosa pine trees. A hierarchical analysis of the population genetic structure showed significant differences between demes on different twigs within individual host trees, between demes on neighboring trees, and between demes in pine plots on adjacent city blocks. Allelic frequencies at a malic enzyme locus were associated with deme-to-deme variation in ecological correlates of insect fitness, suggesting adaptive hypotheses about the causes of population subdivision.     

Increase in hepatic microsomal lipid peroxidation mediated by α-adrenergic system under cold stress and noradrenaline treatment

A membrane protein recognized by monoclonal antibody SQM1 was identified in human squamous carcinomas, including those originating in the head and neck (SqCHN), lung and cervix. Cell lines derived from SqCHN of previously untreated patients expressed high amounts of this protein. In contrast, many cell lines established from SqCHN of patients previously treated with chemotherapy and/or radiation showed diminished amounts of this SQM1 protein. The expression of SQM1 antigen was determined in several SgCHN cell lines made resistant by exposure to methotrexate (MTX) in vitro. The parent cell lines all exhibited strong binding to SQM1 antibody. The MTX-resistant sublines showed much lower membrane binding of SQM1. The lowest SQM1 reactivity was found in cell lines with high resistance to MTX and with diminished rate of MTX transport. Some highly MTX-resistant cell lines which had high levels of dihydrofolate reductase, but which retained a high rate of MTX transport, also retained high levels of SQM1 binding. Reduced SQM1 protein was also found in SgCHN cells which developed resistance to the alkylating drug cis-platinum (CDDP) and which showed reduced membrane transport of CDDP. Cell growth kinetics and non-specific antigenic shifts were not responsible for the differences in SQM1 binding between the parent cell lines and their drug-resistant sublines. The finding of a novel protein which is reduced in cells resistant to MTX and CDDP could contribute to our understanding of the basic mechanisms of drug resistance. By detecting SQM1 protein in clinical specimens, it may be possible to monitor the development of drug resistance in tumors.Abbreviations SqCHN Squamous Carcinoma of the Head and Neck - MTX Methotrexate - CDDP Cis-Platinum - DHFR Dihydrofolate Reductase     

Deficient glycosylation of arylsulfatase A in pseudo arylsulfatase-A deficiency

Summary Deficient arylsulfatase-A activity is diagnostic of a neurodegenerative human lysosomal storage disease, metachromatic leukodystrophy. Paradoxically, similar enzyme deficiency also occurs in normal individuals, who are known as being pseudo arylsulfatase-A deficient. We showed previously that this phenotype is associated with a structural gene mutation that produces an exceptionally labile enzyme. We now report on the nature and consequence of this mutation. When the mutant arylsulfatase-A is deglycosylated by endoglycosidase H, only one smaller molecular species was generated, instead of the two from the normal enzyme. This is consistent with the loss of one of the two N-linked oligosaccharide side chains known to be present on the wild-type enzyme. Quantitative analysis of mannose and leucine incorporation showed that the mutant enzyme incorporated two- to tenfold less mannose than the normal enzyme on a molar basis. This deficient glycosylation was specific to arylsulfatase-A. Another lysosomal enzyme not affected in this mutation, beta-hexosaminidase, was glycosylated normally in the mutant cells. The remaining single oligosaccharide side chain released from the mutant arylsulfatase-A by pronase digestion was normally processed to complex and high-mannose forms. However, the high-mannose side chains contained 30% fewer phosphorylated residues than those of the normal enzyme. Nevertheless, this reduced level of phosphorylation did not prevent targeting of the mutant enzyme to the lysosomes, a process normally mediated through phosphorylated mannose residues. In conclusion, pseudo arylsulfatase-A deficiency is a unique human mutation associated with reduced glycosylation and phosphorylation of a lysosomal enzyme with the loss of one of the two carbohydrate side chains. The mutation results in greatly reduced enzyme stability, thus indicating a role for oligosaccharides in maintaining enzyme stability within the degradative environment of the lysosomes. However, the residual catalytic activity or subcellular targeting of the mutant enzyme was not affected. These properties probably account for the benign clinical presentation of pseudo arylsulfatase-A deficiency.Abbreviations PD Pseudo arylsulfatase-A Deficiency - ARA Arylsulfatase-A     

Degradation of 2-chloroethanol by wild type and mutants of Pseudomonas putida US2

A strain of Pseudomonas putida was isolated that was able to degrade 2-chloroethanol. The degradation proceeded via 2-chloroacetaldehyde and chloroacetate to glycolate. In crude extracts the enzymes for this degradation pathway could be detected. All enzymes proved to be inducible. The dehalogenase that catalyzed the dehalogenation of chloroacetate to glycolate was further characterized. It consisted of a single polypeptide chain with a molecular mass of 28 kDa. After induction the dehalogenase was expressed at a high level. In a mutant resistant to high concentrations of 2-chloroethanol the dehalogenase was no longer expressed. The mechanism of resistance seemed to be due to the inability to convert chloroacetate and export of this compound out of the cell.Non-standard abbreviations CEO 2-chloroethanol - DCPIP 2,6-dichlorophenolindophenol - FPLC fast protein liquid chromatography - PAGE polyacrylamide gelelectrophoresis - PES phenazine ethosulfate - PMS phenazine methosulfate - PQQ pyrroloquinoline quinone     

Induction of vancomycin resistance in Enterococcus faecium by inhibition of transglycosylation

Vancomycin resistance has recently been recognized among clinical isolates of enterococci. Resistance is inducible, and associated with production of a novel 39 kDa membrane protein. The mechanism by which exposure to vancomycin, which does not penetrate the cell membrane, induces resistance is unknown. In the vancomycin resistant strain Enterococcus faecium 228, resistance was also inducible by moenomycin, suggesting that inhibition of the transglycosylation step in peptidoglycan synthesis may be required for induction of resistance. Cytoplasmic pools of peptidoglycan precursors were increased after exposure to vancomycin or moenomycin, representing a potential means for regulation of induction.     

心房钠尿因子对麻醉家兔局部血流的影响

在42只麻醉家兔,观察了静脉注射心房肽Ⅱ(AtriopeptinⅡ,APⅡ)对局部血流量以及动脉内注射 AP Ⅱ 对局部血管阻力的影响。结果如下:(1)静脉注射 APⅡ(30μg/kg)5min后,平均动脉压(MAP)降低11.0±1.5mmHg(n=8,M±SE,下同),与溶剂对照组相比有明显差异(P相似文献